During tomographic imaging of the brain, it is essential that the patient's head be held motionless in an optimal position throughout the procedure. Since an imaging session may require the head to be immobilized for an hour or more, the comfort of the patient is an important factor in achieving a successful examination.
Prior devices for supporting the head during tomographic imaging have typically comprised a trough or dish resting on or extending from a panel or tray on the examination table on which the patient is supported in a supine position. Because heads vary considerably in both size and shape, the trough or dish usually must be provided with a complement of foam pads, which are wedged under and around the head to achieve a head position which is optimal for the examination. The pads also serve to prevent head motion and provide some measure of comfort to the patient. The selection and placement of the pads by the technician can be a time consuming trial and error process which, while usually effective in obtaining the desired head position, is not always effective in immobilizing the head or providing comfortable support for the patient.
The principal shortcoming of previous devices is the reliance on padding for head positioning and restraint. Due to its resilient nature, the padding can allow some head displacement if the patient should twitch, especially if it is not packed tightly enough between the head and head support structure. Since any head movement can blur the image produced, repetition of the procedure may be necessary in some cases.
A further problem with the use of selective padding to position the head is the difficulty in determining whether the comfort level established initially for the patient will be adequate over the lengthy course of the examination. It may turn out, particularly for patients with spinal injuries, that what seemed comfortable at the beginning of the procedure becomes unbearably painful before its completion, necessitating the interruption of the procedure.
In addition to the described problems of inadequate restraint and patient comfort, prior head restraint devices are generally unsuitable for nuclear medicine imaging due to the interference by the head support structure with the imaging radiation. This can create shadows on the image which complicate the reading of the image and could even lead to a misinterpretation of the image.
It is furthermore highly desirable in nuclear medicine imaging, particularly with SPECT (single photon emission computed tomography), to have the camera as close to the patient's head as possible, and prior head support devices generally do not permit the close camera proximity desired.